Patent Literature 1 discloses the nitride semiconductor light emitting device in which an epitaxial layer structure containing AlGaN is less likely to crack. This nitride semiconductor light emitting device includes a support body comprised of a GaN semiconductor, a first conductivity type AlGaN region, a second conductivity type GaN semiconductor layer, and an active layer. Since the c-axis of the GaN semiconductor of the support body extends from one side face to the other side face, the primary surface of the substrate is substantially an m-plane or an a-plane. The AlGaN region and GaN semiconductor layer are provided on the primary surface of the support body. The aluminum composition of the AlGaN region is not less than 0.05 and the thickness D1 of the AlGaN region is not less than 500 nm. The active layer is provided between the first conductivity type AlGaN region and the second conductivity type GaN semiconductor layer.